Communication system



De@ 24, 1946- H. H. scHNECKLoTl-l 2,413,001

COMMUNICATION SYSTEM Filed Sept. 2, 1944 3 Sheets-Skiset 1 /NVEN ro@ H.H. SCH/VECKLOTH ATTORNEY H; H. scHNEcKLcTl-l 2,413,001

COMMUNICATION SYSTEM Filed sept. 2, 1944 s sheets-sneeze,

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POLAR/Z50 ATTORNEY l s sheets-'sheet s H. H. SCHNECKLOTH COMMUNICATIONSYSTEvM Filed Sept. 2, 1944 Dec. 24, 1946.

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Patented Dec. 24, 11946s COMMUNICATION SYSTEM Harry H. Schneckloth,Forest Hills, N. Y., assignor to Bell Telephone Laboratories,Incorporated, New York, N. Y., a corporation of New York ApplicationSeptember 2, 1944, Serial No. 552,418

22 claims. l

This invention relates to telephone systems and particularly to systemscomprising a master ofiice and one or more unattended automatic oiices.

It is the object cf the invention to improve the arrangements fortransmitting alarm signals from unattended automatic oflices to a masteroffice.

It is usual to provide alarm apparatus in an unattended dial cnice whichis effective when a trouble condition exists to seize a trunk to amaster ofce and upon answer of the call by an operator in the masterofficevto transmit a tone signal to indicate that the call is a troublealarm call from 'the unattended oice. It is also known to provide atrouble checking line in the unattended ofce with which connection maybe established on a call from an operato;` or maintenance test man inthe master oflice to determine whether any trouble exists, and thecharacter of the trouble, in the unattended oice.

This invention is an improved alarm arrangement in a system comprisingan attended master office and a plurality of unattended dial oiiiceswhereby on a trouble checking call initiated by an operator in themaster office to any one of the unattended dial oices, signals aretransmitted from the unattended office to operate a visual signalapparatus in the master office indicating that no trouble exists in thedial office or indicating the character of the trouble which does existn the dial oflice, there being a set of such signals in the master omcefor each dial office from which alarm signals are received.

A feature cf the invention is the provision of signal transmittingapparatus in an unattended dial oflice for transmitting to a masteroflice voice frequency signals of different frequencies. One frequencyis used to indicate that no trouble exists in the dial office, and eachof the other frequencies indicates a different kind of trouble in theoffice.

Another feature of the invention is the provision of signal receivingmeans in the master ofce for receiving voice frequency signals of dif--Y ferent frequencies for the different alarm condiv tions which mayexist in a connected dial office and for indicating that no troubleexists in the dial ofce if such is the case.

Another feature of the invention is the provision in an attended oice ofsignal means for indicating whether or not any trouble exists in anunattended automatic oflice, the operation of the signal means beingmaintained for a predetermined length of time after its operation,thereby tion to the specific arrangement and system 1 shown but isgenerally applicable to alarm signaling systems between attended andunattended oices.

Referring to the drawings:

Fig. l shows the alarm signaling apparatus AL in a master oice;

Fig. 2 shows an operators position comprising the cord CDI, a trunkcircuit TCH associated with a trunk TI extending to one unattended dialoffice, and a trunk circuit TG2 l associated with a trunk extending toanother unattended dial office; and

Fig. 3 shows, in an unattended dial office, a trunk circuit TCI2, anincoming selector ISI associated with the trunk circuit TCI2, aconnector Cl and alarm apparatus ALI. Fig. 3 also shows a subscribersstation A, line LI and line circuit LCI, a line nder LFI and a firstselector SI for use in establishing connections on calls originating inthe dial ofce.

The subscriber stations in the unattended dial oflices are of the typeprovided on lines terminating in common battery central offices and eachincludes a dial or other impulse sender for controlling the operation ofautomatic switches through which desired connections are established.The line circuit LCI which comprises a line and a cut-oil relay connectsthe line Ll to terminals in the banks of line finders for originatingtraffic and to terminals in the banks of connector switches similar tothe connector CI for terminating traiiic. The line finder, selector andconnector switches may be of the well-known two-motion step-by-steptype. Reference may be had to Automatic Telephony by Smith and Campbell,2d Edition, pages 53 to 65 for a description of the structure of suchswitches and their operation when used as selectors and connectors.Reference may be had to the patent to R. L. Sto-kely, No. 1,799,654,April 7, 1931, for a description of the operation of a step-by-step linefinder. Each of the switches LFI, SI, ISI and CI is represented in thedrawings by a set of brushes and a single set of terminals, all omittedapparatus being represented by the broken lines connected t the brushes.

The alarm equipment ALI comprises a line relay connected to the tip andring terminals of the terminal set I 5i! in the banks of a group ofconnectors including the connector CI, a transformer |52, alarm relays|62, |63 and |54 and sources lli, |12, VI`|3 land Il@ of alternatingcurrent of frequencies FI, F2, F3 and F4 respectively. Ii there is notrouble condition existing in the dial oiice shown in Fig. 3 nonerofrelays |52, |63 or lrl is operated. Rel-ay I 62 is operated when anyfuse in the dial oiice has burned out; relay E53 is operated when apermanent signal condition exists in the dial office; and relay |53 isoperated when any other alarm condition exists in the dial office.

The trunk circuit TC! I, terminating trunk TI in the master cinc-e andthe trunk circuit TC|2 terminating the trunk TI in dial office are shownin detail and the operation of each of these trunk circuits ishereinafter described on calls in both directions. The trunk circuitTCZI terminating a trunk to a second dial oiice is similar to the trunkcircuit TCE I. The cord CDI and the operators dial and telephone areshown schematically and may be similar to the cord and positionequipment disclosed in detail in the patent to King and Miller No.2,203,765 granted July 23, 1940.

The alarm equipment AL in the master cnice comprises signal receivingrelays II, 2|, 3| and lll selectively connected by lters IB, 28, 3i] and4|) to the jack J I. Each of the filters is tuned to pass current of adiierent one of the frequencies used for transmitting alarm signals froman unattended dial oce to the master oiiice. The alarm apparatus ALfurther comprises alarm apparatus individual to each unattended oiiicefrom which alarm signals may be received. The ala-rm apparatusindividual to dial olice I comprises keys KII and KIZ, gas-filleddischarge lamps LII to Llfl, and a timing relay TRI; the alarm apparatusfor a second dial oilce comprises keys KZi and X22, gas-filled dischargelamps L2! to L24, and a timing relay TR2. The lamps LI| and LEI areprovided for indicating that there is no trouble existing in thecorresponding dial office; the lamps L|2 and L22 are provided forindicating a fuse alarm condition in the corresponding oice; the lampsLI 3 and L23 are provided for indicating a permanent signal condition inthe corresponding dial oce; and the lamps LI li and L24 are provided forindicating any other alarm condition which may exist in thecorresponding dial omce. The timing relays TRI and TR2 are aranged tooperate a predetermined interval, for instance, half an hour after thelighting of any of the associated lamps, so as to extinguish the lampand thereby indicate that it is time to again check the alarm conditionsexistingin the corresponding unattended dial office.

The voltage of the .battery B2 normally connected in series with thewinding of each of the timing relays and the associated lamps isinsucient to effect breakdown of any lamp but is suicient to maintainthe energization of any lamp after breakdown until the associated timingrelay opens the circuit therethrough. With key KII or -KZI actuated andwith any one of relays li, 2|, -35 or lll operated, the voltage ofbatteries BI and B2 in series is sunicient to break down the lampcorresponding to the operated one of relays lI, 2|, 3| and 4I in the setof lamps 4 associated with the operated one of keys KI I and KEI.

Assume now that a call is originated at station A, that the line finderLFI is operated to extend the calling line to a first selector SI andthat the selector SI is actuated in response to the dial impulsescreated by the dialing of the iirst digit of the called subscribersnumber to select the terminals .connecting to trunk circuit TCI2. Whenthe cut-through relay (not shown) of the selector SI operates to extendthe connection from the conductors of line LI to conductors I 0I and |02of trunk circuit TCI2, the line relay I II of trunk circuit TCI2 isoperated by the curent in a circuit traced from battery through theupper winding of relay IIl, a lower back contact of relay |59,

lower right winding of repeating coil I I 0, another lower back contactof relay |69, conductor |52, middle brushes of selector SI and line nderLFI, lower conductor of line LI, through the telephone at station A, theother conductor of line LI, top brushes of line finder LFI and selectorSI, conductor It! I, an upper back contact of relay |59, upper rightwinding of repeating coil I I0, another upper back contact of relay |09and through the lower winding of relay I I I to ground. Relay I I lcloses a circuit for operating relays |35 and H2. Relay |55 connectsground to conductor |03 to hold the switching relay (not shown) ofselector SI and to guard the trunk circuit TC l 2 against seizure lbyany other selector having access thereto. Relay II2 connects ground toconductor MSl to start the ringing machine motor (not shown) and closesa connection from the ringing source RG through condenser |55 and a backContact of relay |84 to conductor IDI so as to transmit a ringing toneto the calling subscriber as -an indication that the operator in themaster oice is being signaled. The operation of vrelay |I2 interchangesthe connections between the windings of relay II3 and the conductors oftrunk TI leading to the master office, thereby reversing the currentthrough `these conductors to effect the operative energization of bothwindings of the polarized relay 5I of trunk circuit TC! I. Although thewindings of relays II3 and 5I are normally connected in a closed circuitover trunk T! the .current in this circuit is not strong enough tooperate the marginal relay IIS and is in the non-operate direction withrespect to relay 5I, The circuit for operating relay 5I may be tracedfrom battery through the lower winding of relay IIB, a front contact ofrelay IIE, upper left winding of repeating coil IIB, upper conduc- `torof trunk TI, upper` back contact of relay 62, upper right winding ofrepeating coil 59, both windings of relay 5I, lower right winding ofrepeating coil 59, lower conductor of trunk TI, lower left winding oirepeating coil III), a front Contact of relay l I2, and through theupper winding of relay IIS to ground. The operation of relay 5I closes acircuit for operating relay 52. Relay 52 closes a circuit for lightingthe multiple answering lamps 53 and a circuit Yfor operating relay 54.Relay 54 closes a circuit for operating relay 55. Relay 55 closes acircuit for lighting the multiple busy lamps 51 and connects a busypotential through resistor 55 and the upper winding of relay 5l to thesleeve of jack J Ill.

When an operator answers the call by inserting vthe plug P2 of a cordCD5 in jack JIG, a circuit and jack J-I and the lower, high-resistancewinding of relay 5i to ground. Relay 51 oper- S ates closing a circuitfor operating relay 58. Relay 58 closes a circuit for operating relay6|; closes a short-circuit around the upper, high-resistance winding ofrelay I thereby causing the operation of relay IIS of trunk circuitTCI2; opens the busy potential connection between resistor 5B and thesleeve of jack JIU; and opens the circuit through the winding of relay52 to release this relay and thus extinguish lamp 53. Relay 6I closes aholding circuit for relay 55 and completes the talking connectionbetween the left windings of repeating coil 55 and the line conductorsof jack J II).

The aforementioned operation of marginal relay I I3 of trunk circuitTCIZ when the call is answered by an operator in the master oice, closesa circuit for operating relay Izlel. Relay Imi disconnects condenser ISGfrom conductor IIlI to end the transmission of ringing tone to thecalling subscriber, disconnects ground from the ringing-machinemotor-start conductor MS, and closes a circuit ior holding relay m5. Thetalking connection between the calling line and the operator in themaster oiiice includes the repeating coils 59 and IIB and the connectionis under the joint control of the calling subscriber and the answeringoperator. When the calling subscriber releases the connection, relay IIl releases.

The release of relay I II causes the release of relay II2, therebyrestoring the current over trunk TI to its normal direction to eiiectthe release of relay 5I of trunk circuit TCII in the'master office,After relay III releases, relay I55 is held under the joint control ofrelays H3 and Iill. The release of relay 5I of trunk circuit TCI Iconnects ground to the upper, low-resistance winding of relay 5l,thereby causing the lighting of the supervisory lamp in the operatorscord circuit as a disconnect signal. When the plug P2 of cord CDi isdisconnected from jack JIE, relay 5l releases. The release of relay 5lcauses the successive release of relays 53 and 6I. Relay 52 reoperatesif relay 5I has not yet released. The release of relay 53 opens theshort-circuit around the upper, high-resistance winding of relay 5Ithereby causing the release of relay H3 of trunk circuit TCI 2. Therelease of both of relays III and I I3 in trunk circuit TCIZ causes therelease of relays IM and HB5. Relay I5 disconnects ground potential fromconductor HB3 to cause the release of the selector SI and the return ofthe selector SI and line finder LFI to normal. The release of relay bldreconnects conductors I3I and |32 to the line relay (not shown) of theincoming selector ISI, thereby preparing trunk TI for seizure on anothercall in either direction.

Assume next that the operator in the master oilice connects the plug P!of cord CDI with jack J I associated with the alarm equipment AL andconnects the plug P2 with jack J I9 to make a call to dial oice I. Relay5l operates in a circuit including the sleeve conductors of jack J Itand plug P2 to battery in the operators position circuit. Relay closes acircuit for operating relay 58. Relay 55 closes a short-circuit aroundthe upper winding of relay 5I to eiect the operation of relay M3 oftrunk circuit TCIZ, closes a circuit for operating relay 5I, andconnects ground to the upper winding or relay 5l to eiect the lightingof the supervisory lamp in the cord circuit CDI. Relay 5I closes acircuit for operating relay 5a; closes a connection from the winding ofrelay 54, through the upper left winding of repeating coil 59, to thetip conductor of jack J I0; and closes a connection from ground at theouter lower front contact of relay 58, through resistor 6B, upper backcontact of relay 54,inner upper front contact of relay 6I and lowerright winding oi repeating coil 59, to the ring conductor oi' jack J I.The operation of relay 54 closes a circuit for operating relay 55; andrelay 55 lights the multiple busy lamps 5l, The operation of relay I I 3of trunk circuit TCIZ closes a circuit, including back contacts ofrelays m5 and i I2, through the winding of relay HB9. Relay I B9operates thereby connecting its winding to sleeve conductor |33 of theassociated incoming selector ISI and extends ground potential toconductor H13 to mark the trunk circuit TCI2 as busy in the banks ofselectors having access thereto. Relay H39 closes a bridge comprisingthe winding of relay Il and resistor II5 in parallel across conductorsISI and |32 of selector ISI to operate the line relay (not shown) toprepare the selector for operation by dial impulses. The selector ISIconnects holding ground potential to sleeve conductor I33 in usualmanner to hold relay I 09.

When the calling operator operates the position dial key (not shown), acircuit for operating relay 6G is closed from battery in the positioncircuit OP through the tip conductors of plug P2 and jack J Ill, a frontcontact relay 6I, upper left winding of repeating coil 53 and thewinding of relay 54 to ground. Relay 54 operates, closing a circuit foroperating relay and connecting the tip of jack J I0 through repeatingcoil 59 to the winding of relay 54, independent of the contact of relay6I. Relay 65 closes a circuitvior holding relay 54 operated and closes acircuit from ground through the upper winding of relay 52, winding ofrelay 63, lower front contact of relay 55, lower left winding ofrepeating coil 59, ring conductors of jack J I5 and plug P2, through theimpulse contacts of the operators dial, to battery. Relays'BZ and 63operate. Relay S2 locks under control of relays 64 and 58 and opens thecircuit through the winding of relay 6 I. The release of relay 6Idisconnects the ring conductor of jack J I0 from condenser 5B andshort-circuits the upper winding of relay B2 to prepare relay 53 forresponse to dial impulses. Relay 62 is held operated by the energizationof its lower winding in a circuit including its lower front contact, afront contact of relay 64, and a front contact of relay 53. With relays63 and G2 operated, the impulse repeating contacts of relay 63 areconnected across the conductors of trunk TI in place of the bridgecomprising the lower winding oi relay 5I. When the operator dials thedigits of a called subscribers number, relay 63 is alternately releasedand reoperated responsive to the dial impulses of each train therebycreated. Corresponding impulses are transmitted by the contacts of relay63 over trunk TI to relay II3 of trunk circuit TC I 2. When dialing iscompleted, the restoring of the operators dial key disconnects batteryfrom the tip of the cord, releasing relay 65. Relay 64 opens theconnection between repeating coil 59 and the tip of jack J I5,shortcircuits the contacts of relay 63, and releases relays 65 and 62.The release of relay G5 disconnects the winding of relay 53 from thering con- 'ductor of jack J Il! and opens the holding circuit of` relay54. The release of relay 62 disconnects the contacts of relay 53 fromthe conductors of trunk TI and reestablishes the bridge, comprising thelower winding of relay 5I, across these conductors. The release of relay52 causes the reoperation of relay 5I and the completion of the talkingconnection between jack J I0 and repeating coil 59. The reoperation ofrelay 6| recloses the circuit for operating relay 54. Since relay 55 isslow in releasing, it remains operated during the transfer of theconductors of trunk TI to and from dialing conditions.

In response to the dial impulses thus transmitted over trunk TI by thecontacts of relay 63, relay IIS of trunk circuit TCIZ is alternatelyreleased an'd reoperated. When relay IIS releases in response to thefirst impulse of each train, it opens the bridge across conductors ISIand |32 and closes a circuit including a back contact of relay I I2 anda front contact of relay |59 for operating the sloW-to-release relayIe'I. With relay II operated, the reoperation of relay IIS closes abridge comprising resistor |38 across conductors I 3| and |32 in placeof the bridge com-l prising the winding of relay IILI. Relay IQ'I is.slow to release and remains operated while a train of impulses is beingrepeated by relay IIS. The release of relay |21, when relay IIS remainsoperated at the end of a train of impulses, reconnects the Winding ofrelay li across conductor: ISI and |32 for response to supervisorysignals.

The first train of impulses repeated by reiayc 63 and I I3 controls theoperation of the incozr ig; selector ISI to select a corresponding groupof terminals. The selector ISI is thereupon operated automatically toselect an idle set of terminals in the selected groupl which terminalsare connected to a connector CI. The impulses created by the dialing ofthe last two digits of the called number are repeated by relays |33 andH3 to the line relay ILlI of a connector CI to selectively operate theconnector and thereby complete a connection with the called lineterminals. If the called line is idle, the called station is signaled inusual manner; and, if the call is answered, relay Idd is operated toreverse the direction of current through conductors ISI and |32 tooperate relay IIII. Relay II4 closes a circuit for operating relay IIZ;and relay II2 eects the reversal of current through conductors of trunkTI to operate relay 5I of trunk circuit TCI I. The operation of relay 5Idisconnects ground from the upper winding of relay 5l to extinguish thesupervisory lamp in the operators cord circuit. The talking connectionbetween the operator and the called subscriber includes the repeatingcoils 5e and I I5 and is under the sole control of the operator.

If the called subscriber restores the telephone to normal before theoperator disconnects, relay |44 releases so as to restore the directionof current through conductors I3I and |32 and thereby cause thesuccessive release of relays I I 4, I I2 and 5 I, and the lighting ofthe supervisory 'lamp in the operators cord circuit. When the operato-1'disconnects, relays 51, 58, 3|, 54 and 55 are released. The release ofrelay 5% opens the sliertcircuit around the upper Winding of relay 5Ithereby causing the release of marginal relay I I3 in trunk circuitTCI2. The release of relay IIS opens the operating circuit of relayV|639 and opens the bridge across conductors I 3| and |32 thereby causingthe release of the incoming selector ISI and the release of theconnector CI. If the called subscriber has failed to disconnect, theVconnector is held operated but the incoming selector ISI is restored tonormal in the usual manner. When the called subscriber releases, theconnector switch is also restored to normal in usual and Well-knownmanner.

Assume next that the connector CI has been selectively operated by dialimpulses corresponding to the last two digits of the called number toselect the trouble checking terminals |50 associated with the alarmequipment ALI. In this case the bridge consisting of the Winding ofrelay I5| and left winding of transformer |52 effects the tripping ofthe ringing and closure of the talking circuit through the connector CIin usual manner. If at the time relay I5I operates there is no troubleexisting in this dial oiice, none of relays |62, ||I3 and |64 areoperated; and a circuit is closed from the alternating current sourceI'II of frequency FI through a back contact of each of relays |62, |63and IE5 in series, a front contact of relay I5I, and the right windingof transformer |52 to transmit current of frequency FI throughtransformer |52 and the talking conductors of connector CI, selectorISI, trunk circuit TCI2, trunk TI, trunk circuit TCII and cord CDI, tothe alarm equipment AL in the master office. The current thustransmitted is transmitted through lter I0 to operate relay iI withouteffecting the operation of any one oi relays 2|, 3| or 4I. If fuse alarmrelay |62 is operated, current of frequency F2 is transmitted fromsource |72 through transformer |52 and the talking connection to effectthe operation of relay 2| of alarm apparatus AL in the master oflice,the filter being tuned to pass current of frequency F2. If the permanentsignal alarm relay |63 is operated, current of frequency F3 istransmitted from source |13, through transformer |52 and the talkingconnection to alarm apparatus AL to eiect the operation of relay 3|,filter 30 being tuned to pass current of frequency F3. "And, if othertrouble conditions exist in oiiice I such as failure of the ringingequipment, relay |64 is operated and current of frequency FII istransmitted from source I'III, through transformer |52 and the talkingconnection to alarm apparatus AL to operate relay 4|, the nlter 40 beingtuned to pass current of frequency F4. The operator noW momentarilyactuates key KI I to connect the signal lamps LII, LIZ, LIS and LIII toconductors I2, 22, 32, 42, respectively.

' The voltage thus applied across the lamp corresponding to the operatedone of relays II, 2|, 3| and 4I is high enough to cause ionization. ofthe gas in that lamp. The operator may then release key KII anddisconnect the cord CDI from jacks J I and J I0, the voltage of batteryB2 being sufficient to maintain the energization of any one of thesignal lamps LII to LI II which has been energized. Thus a continuingsignal indicative of the maintenance conditions in the oflice I is givenuntil the timing relay TRI operates. This relay is designed to operatein series with any one of the signal lamps at the end of a desiredinterval, for instance half an hour. The operation of relay TRIextinguishes the lighted lamp, thereby indicating to the operator that acheck of the alarm conditions at the dial ofiice has not been madeWithin this interval. An energized signal lamp may be extinguished priorto the operation of relay TRI by the operation of the release key KIZ.

A check of the conditions existing in dial office 2 may be made byconnecting a cord CDI to jacks J I and J ZI), dialing the troublechecking number for dial office 2 and operating key K2I, therebyeffecting the lighting of that one of lamps L2! to L24 which correspondsto the condition existing in dial ofce 2 in similar manner to that inwhich the alarm lamps for dial cnice I are energized as above described.

What is claimed is:

1. In a telephone system, an unattended dial olce, a master oliice,alarm apparatus in the unattended oflice responsive selectively to aplurality of trouble conditions, signal receiving means in the masteroi'lice, means including an interofce trunk for connecting said signalreceiving means to said alarm apparatus, and a set of alarm signals insaid master oiice controlled by said signal receiving means for visuallyindicating the existence of any of said plurality of trouble conditionsin the unattended oiice.

2. In a telephone system, an unattended dial oiiice, an attended oflice,signal sending means in said unattended office for selectively sending asignal of a first character when no trouble exists in the unattended oceand for sending a signal of a second character when a trouble conditionexists in the unattended cmce, signal receiving means in said attendedolice for selectively responding to signals of said rst and secondcharacters, means comprising a trunk between said olices connecting saidsignal receiv ing means to said signal sending means, and visual signalmeans selectively controlled by said signal receiving means.

3. In a telephone system, an unattended dial office, an attended oiiice,signal sending means in said unattended ofce for selectively sending asignal of a rst character when no trouble exists in the unattendedoffice and for sending a signal of a second character when a troublecondition exists in the unattended office, signal ren ceiving means insaid attended oince for selectively responding to signals of said firstand sec ond characters, means comprising a trunk between said ofcesconnecting said signal receiving means to said signal sending means,signal means selectively energized by said signal receiving means toindicate the condition existing in the unattended oice, and means formaintaining the energization of said signal means after the connectionbetween said signal sending and signal receiving means is ended.

4. In a telephone system, an unattended dial oflice, an attended oiiice,signal sending means in said unattended oiiice for selectively sending asignal of a rst character when no trouble exists in the unattended oiiceand for sending a signal of a second character when a trouble conditionexists in the unattended cnice, signal receiving means in said attendedoffice for selectively responding to signals of said ilrst and secondcharacters, means comprising a trunk between said oices connecting saidsignal receiving means to said signal sending means, signal meansselectively energized by said signal receiving means to indicate thecondition existing in the unattended oice, means for maintaining theenergization of said signal means after the connection between saidsignal sending and signal receiving means is ended, and means forterminating the energization of said signai means a predeterminedinterval of time after the connection between said signal sending andsignal receiving means is ended.

5. In a telephone system, an unattended dial oce, an attended office,signal sending means in said unattended oce for selectively sending asignal of a iirst character when no trouble exists in the unattendedoffice and for sending a signal of a second character when a troublecondition exists in the unattended ofce, signal receiving means in saidattended oiice for selectively responding to signals of said rst andsecond characters, means comprising a trunk between said oiicesconnecting said signal receiving means to said signal sending means,signal means selectively energized by said signal receiving means toindicate the condition existing in the unattended oiice, means formaintaining the energization of said signal means after the connectionbetween said signal sending and signal receiving means is ended, meansfor terminating the energization of said signal means a predeterminedinterval of time after the connection between said signal sending andsaid signal receiving means is ended, and other means for ending theenergization of said signal means,

6. In a telephone system, an unattended dial oflice, an attended omce, atrunk between said olces for use in completing connections betweencalling and called lines, means in said unattended oflice for sendingany one of a plurality of signals each of a different character, meansin said unattended cnice preparing said signal sending means to send asignal of one character when no trouble condition exists in saidunattended oice and for selectively preparing said signal sending meansto send a signal of a different character when a trouble exists in theunattended office, the character of the signal depending on thecharacter of the trouble, signal receiving means in the attended officefor selectively responding to a signal of any one of said characters,means comprising said trunk for connecting said signal receiving meansto said signal sending means, and visual signal means in said attendedoiiice selectively controlled by said signal receiving means.

7. In a telephone system, an unattended dial cnice, an attended oice, atrunk between said. offices for use in completing connections betweencalling and called lines, means in said unattended omce for sending anyone of a plurality of signals each of a difierent character, means insaid un attended office preparing said signal sending means to send asignal of one character when no trouble condition exists in saidunattended office and for selectively preparing said signal sendingmeans to send a signal of a diierent character when a trouble exists inthe unattended ofce, the character of the signal depending on'thecharacter of the trouble, signal receiving means in the attended ofcefor selectively responding to a signal oi any one of said characters,means comprising said trunk for connecting said signal receiving meansto said signal sending means, visual signal means in said attendedoilice selectively controlled by said signal receiving means to indicatethe condition existing in the unattended omce, and means for maintainingthe energization of said signal means after the connection between saidsignal sending and signal receiving means is ended.

8. In a telephone system, an unattended dial office, an attended oiiice,a trunk between said olices for use in completing connections betweencalling and called lines, means in said unattended ofce for sending anyone of a plurality of signals each oi a different character, means insaid unattended omce preparing said signal sending means to send asignal of one character when no trouble condition'exists in saidunattended office and for selectively preparing said signal sendingmeans to send a signal of a different character when a trouble exists inthe unattended oiiice, the character of the signal depending on thecharacter of the trouble, signal receiving means in the attended oiicefor selectively responding to a signal of any one ofv said characters,means comprising said trunk for `connecting said signal receiving meansto said signal sending'means, visual signal means in said attendedofceselectively controlled by said signal receiving means, signal meansselectively energized by said signal receiving means to indicate thecondition existing in the unattended oiiice after the connection betweensaid signal receiving means is ended, and means for terminating theenergization of said signal means a predetermined interval of time afterthe connection between saidA signai sending and signal receiving meansis ended.

9. In a telephone system, an unattended dial oflice, an attended office,a trunk between said oiices for use in completing connections betweencalling and called lines, means in said unattended oice for sending anyone of a plurality of signals each of a different character, means insaid unattended cnice preparing said signal sending means to send asignal of one character when no trouble condition exists in saidunattended ofnce and for selectively preparing saidsignal sending meansto send a signal of a different character when a trouble exists in theVunattended ofce, the character of the signal depending on the characterof the trouble, signal receiving means in the attended oice forselectively responding to a signal of any one of said characters, meanscomprising said trunk for connecting saidsignal receiving means to saidsignal sending means, visual signal means in said attended oiilceselectively controlled by said signal receiving means to indicate thecondition existing inthe unattended oiiice, means for maintaining theenergization of said signal means after theconnection between saidsignal sending and signal receiving means is ended, means forterminating the energization of said signal means a predeterminedinterval of time after the connection between said signal sending andsignal receiving means is ended, and other means for ending theenergization of said signal means.

l0. In a telephone system, a plurality of unattended oices, an attendedoice, trunks betweensaid attended oince and each of said unattendedoiices, like means in each of said unattended ojces for sending a signalof one character when no trouble condition exists in the unattendedcnice and a signal of a different character when a trouble conditionexists in the unattended oiiice, signal receiving means in theunattended ofiice for selectively responding to a signal of eithercharacter, means comprising said trunks for connecting said signalreceiving means to the signal sending means in any desired one of saidunattended oiiices, like signal means in said attended oiiice for eachof said unattended oiilces arranged for selective control by said signalreceiving means, and means for connecting the signal receiving means tothe signal means corresponding to the unattended cnice the signalsending means of which is connected to said signal receiving means,thereby to effect the selective energization of the signal means.

1l. In a telephone systema plurality of unattended l ofiices, anattended pince, trunks between said .attended oiilce and each of saidunattended oices, like means in each ofA said unattended ofces forsending a signalofone Acharacterwhen no trouble condition exists in-theunattended'oiiice and ya'sienal oa different character when a troublecondition exists in the unattended office, signal receiving means in theunattendedoce'for selectively responding to a signal of eithercharactergmeans comprisingsaid trunks for connecting said signal receiving meanstothe signal sending means in any desiredoneof said unattended ofces,like signal means in said attended cnice for each of said unattendedoffices arranged for selective control by said signal receiving means,means for connecting the signal receiving means to the signal meanscorresponding to the unattended oice the signal sending means of whichis connected to said signal receiving means, thereby to eiect theselective energization of the signal means, and means in said attendedoiiice for each of said signal means for maintaining the energization ofthe associated signal means after the connection between the signalreceiving means and the signal sending means ofthe correspondingunattended oilice is terminated.

12. In a telephone system, a plurality of unattended oiiices, anattended oice, trunks between said attended oihce and each of saidunattended offices, like means in each of said unattended cnices forsending a signal of one character when no trouble condition exists inthe unattended office and a signal of a diierent character when atrouble condition exists in the unattended office, signal receivingmeans in the unattended oilice for selectively responding to a signal ofeither character, means comprising said trunks for connecting saidsignal receiving means to the signal sending means in any desired one ofsaid unattended omces, like signal means in said attended office foreach of said unattended offices arranged for selective control by saidsignal receiving means, means for connecting the signal receiving meansto the signal means corresponding to the unattended oiiice the signalsending means of which is connected to said signal receiving means,thereby to eiect the selective energization oi the signal means, meansin said attended ofce for each of said signal means for maintaining theenergization of the associated signal means after the connection betweenthe signal receiving means and the signal sending means of thecorresponding unattended oice is terminated, and like means in saidattended ofce for each of said signal means for terminating theenergization of the associated signal means a predetermined interval oftime after the connection between said signal receiving means and thesignal sending means of the corresponding unattended ofce is terminated.

13. In a telephone system, a plurality of unattended oiiices, anattended oce, trunks between said attended oiiice and each of saidunattended oices, like means in each of said unattended ofces forsending any one of a plurality of signals each oi a different character,alarm means in each unattended ofce preparing the signal sending meansto send a signal of one character when no trouble exists in theunattended oiiice and for :preparing the signal sending means to send asignal of a different character when a trouble exists in the una tendedofnce, the character of the signal depending on the character of thetrouble, signal receiving means in the attended oiiice for selectivelyresponding to a signal of any one of said characters, means comprisingsaid trunks for connecting said signal receiving means to the signalsending means in any desired one of said unattendedofces, sets of signaldevices in said attended ofce, one set for each unattended ofce, andmeans for connecting said signal receiving means to the signal setcorresponding to the unattended4 oiiice the signal sending means ofwhich is connected to said signal receiving means, thereby to eiect theselective energization of said set of signal devices.

14. In a telephone system, a plurality of unattended offices, anattended ofce, trunks between said attended office and each of saidunattended offices, like means in each of said unattended offices forsending any one of a plurality of signals each of a different character,alarm means in each unattended cnice preparing the signal sending meansto send a signal of one character when no troullcle exists in theunattended oiiice and for preparing the signal sending means to send asignal of a.' different character when a trouble exists in theunattended oiiice, the character of the signal depending` on thecharacter of the trouble, signal receiving means in the attended officefor selectively responding to a signal of any one of said characters,means comprising said trunks for connecting said signal receiving meansto the signal sending means in any desired one of said unattendedoffices, sets of signal devices in said attended oiiice, one :set foreach unattended oiiice, means for connecting said signal receiving meansto the signal set corresponding to the unattended office the signalsending means of which is connected to said signal receiving means,thereby to effect the selective energization of said set of signaldevices, and means in said attended office for each of said sets ofsignal devices for maintaining the energizetion of the associated set ofsignal devices after the connection between the signal receiving meansand the Signal sending means of the corresponding unattended office isterminated.

15. In a telephone system, a plurality of unattended ciiices, anattended oiiice, trunks between said attended office and each of saidunattended offices, like means in each of said unattended onices forsending any one of a plurality of signals each cf a. differentcharacter, alarm means in each unattended office preparing the signalsending means to send a signal of one character when ne trouble existsin the unate tended oihce and for preparing the signal sending means tosend. a signal of a different chai acter when a trouble exists in theunattended oiiice, the character of the signal depending on thecharacter of the trouble, signal receiving means in the attended oihcefor selectively respending to a signal of any one of said characters,means comprising said trunks for connecting said signal receiving meansto the signal sending means in any desired one of said unattendedoflces, sets of signal devices in'said attended office, one set for eachunattended office, means for connecting said signal receiving means tothe signal set corresponding to the unattended oliice the signal sendingmeans of which is connected to said signal receiving means, thereby toeffect the selective energization of said set of signal devices, meansin said attended oflice for each of said sets of signal devices formaintaining the energication of the associated set of signal devicesafter the connection between the signal receiving means and the signalsending means of the corresponding unattended ciiice is terminated, andlike means in said attended odi-ce for each of said sets of signaldevices for terminating the enerw gizaticn of the associated signaldevices a predetermined interval of time after the connection betweensaid signal receiving means and the signal sending means of thecorresponding unattended oiiice is terminated.

16. In a telephone system, an attended oiiice,

an unattended o'ice, a trunk I'between said ofiices for completingconnections between calling and called lines in said omces, signalreceiving means in said attended cnice, a trouble checking line in saidunattended cnice, means including said trunk for connecting said signalreceiving means to said trouble checking line, signal sending meansassociated with said line comprising a source of current of a firstfrequency and a source of current of a second frequency, meanscomprising a trouble alarm relay in said unattended oice for connectingthe source of the first frequency to said signal sending means when notrouble exists and for connecting the source of the second frequency tosaid signal sending means when trouble exists in said unattendedoii'ice, said signa-l receiving means comprising two relays and ltersfor selectively transmitting current of a diiferent one of saidfrequencies to each of said relays, a signal device for operation whenno trouble exists in the unattended office and a signal device foroperation when trouble exists in the unattended office, and means forconnecting said devices to said signal receiving means thereby to effectthe operation of the one or the other of said signal devices accordingto Whether or not trouble exists in the unattended oince.

17. In a telephone system, an attended oce, an unattended oice, a trunkbetween said offices for completing connections between calling andcalled lines in said oflices, signal receiving means in said attendedoice, a trouble checking line in said unattended oiiice, means includingsaid trunk for connecting said signal receiving means to said troublechecking line, signal sending means associated with said line comprisinga source of current of a first frequency and a source of current of asecond frequency, means comprising a trouble alarm relay in saidunattended oiiice for connecting the source of the iirst frequency tosaid signal sending means when no trouble exists and for connecting thesource of the second frequency to said signal sending means Vwhentrouble exists in said unattended omce, said signal receiving meanscomprising two relays and ilters for selectively transmitting current ofa diierent one of said frequency to each of said relays, a signal devicefor operation when no trouble exists 'm the unattended cnice and asignal device for operation when trouble exists in the unattendedoffice, means for connecting said devices to said signal receiving meansthereby to eiect the operation of the one or the other of said signaldevices according to whether or not trouble exists in the unattendedoice, and means for maintaining the operation of either one of thesignal devices for a predetermined interval after the connection betweensaid signal receiving means and said trouble checking line isterminated.

18. In a telephone system, an attended oice, a plurality of unattendedoflices, each comprising lines including a trouble checking line andswitches for seizing called lines, trunks between said attended and eachof said unattended ofnces, signal receiving means in said attended ofce,means including said trunks and switches for connecting said signalreceivingv means to said trouble checking lines, one at a time, likesignal sending means in each of said unattended ofiices associated withsaid trouble checking lines respectively, each of said signal sendingmeans comprising a transformer, a plurality of sources of alternatingcurrent each of a 'diierent frequency, a plurality of alarm relays eachoperated 115 when 'a diierent trouble condition exists inthe cnice inwhich the alarm relaysare located and means including said relays forconnecting one of said sources to said transformer when no 'troublecondition exists in the office and for connecting another and diierentone of `said sources to said transformer when each dilTerent troublecondition exists inthe oiice, means rsponsive to seizure of said troublechecking line for completing a connection from said line through isaidtransformer to one of said sources according to what if any trouble thenexists in the oice, thereby to selec- -tively transmit to said signalreceiving means a signal indicative of the condition existing in theoiiice, said signal receiving means comprising a plurality of relays onefor each different signal which may be transmitted from the signalsending means of a connected one of said trouble checking lines, ltersfor selectively transmitting current of a different one of saidfrequencies to each of said rela-ys, respectively, sets of signaldevices, one set for each of said unattended ofces and each setincluding a device for each signal which may be received from thecorresponding unattended oiice, means individual to each set of signaldevices for operatively con-` necting said devices to said signalreceiving means, thereby to effect the operation of the signaldevicecorresponding to the condition Vexisting in the unattended oiiice towhich the signal receiving means is then connected.

19. In a telephone -system,an attended office, an unattended oice, atrunk between said ofces for completing connections between calling andcalled lines in said oices, signal receiving means in said attendedomce, a trouble checking line in said unattended oiiice, means includingsaid trunk for connecting said signal receiving means to said troublechecking line, signal sending means associated with said line comprisinga source of current of a first frequency and a source of current of asecond frequency, means comprising a trouble alarm relay in saidVunattended oce for connecting the source of the rst frequency to saidsignal sending means when no trouble exists in said unattended o'ce andfor connecting the source of the second frequency to Said signal sendingmeans when trouble exists in said unattended ofnce, said signalreceiving means comprising two relays and lters for selectivelytransmitting current of a different one of said frequencies to each ofsaid relays, a gas-filled discharge lamp for operation when no troubleexists in the unattended oice and a gas-'lled discharge lamp foroperation when trouble exists in the unattended oice, and'means'for'connecting said lamps to said signal'receiving'means thereby toeffect the energization of one or theo'ther of said lamps according towhether or not trouble exists in the unattended oirlce.

20. Ina telephone system, an attendedoliica an unattended oiicega trunkbetween'said offices for completing connections `between calling andcalled lines in said oidces, signallreceiving means in said attendedofce, a trouble checking line in said unattended oiice, means includingsaid trunk for connecting said signal receiving means to said troublechecking linea signal sending means associated with said line comprisinga source of current of a 'first fleqllerly and a source of Vcurrent of alsecond frequency, .means comprising a trouble alarm relay in saidunattended oice for connecting fthe source of the first frequency tosaid `signal sending .means when no trouble exists in said unattendedoiice and for connecting the source of the Second frequency to saidsignal sending means when trouble exists in said unattended office, saidsignal receiving means comprising two relays and filters for selectivelytransmitting current of a different one of said frequencies to each ofsaid relays, a gas-filled discharge lamp for operation when no troubleexists in the unattended oiice and a gaslled discharge lamp foroperation when trouble exists in the unattended office, means forconnecting said lamps to said signal receiving means thereby to effectthe energization of one or the other of said lamps according to Whetheror not trouble exists in the unattended ofce, and means for maintainingthe energization of either one of said lamps for a predeterminedinterval after the connection between said signal receiving means andsaid trouble checking line is terminated.

21. In a telephone system, an attended office, a plurality of unattendedoices, each comprising lines including a trouble checking line andswitches for seizing called lines, trunks between said attended and eachof said unattended oices, signal receiving means in said attended ofce,means including said trunks and switches for connecting said signalreceiving means to said trouble checking lines, one at a time, likesignal sending means in each of said unattended oices associated withsaid trouble checking lines respectively, each of said signal sendingmeans comprising a transformer, a plurality of sources of alternatingcurrent each of a different frequency, a plurality of alarm relays eachoperated when a different trouble condition exists in the oiice in whichthe alarm relays are located and means including said relays forconnecting one of said sources to said transformer when no troublecondition exists in the office and for connecting another and differentone of said sources to said transformer when each different troublecondition exists in the oii'ice, means responsive to seizure of saidtrouble checking line for completing a connection from said line throughsaid transformer to one of said sources according to what if any troublethen exists in the oiiice, thereby to selectively transmit to saidsignal receiving means a signal indicative of the condition existing inthe oiilce, said signal receiving means comprising aplurality of relaysone for each different signal which may be transmitted from the signalsending means of a connected one of said trouble checking lines, iiltersfor selectively transmitting current of a different one of saidfrequencies to each of said relays respectively, sets of gaslleddischarge lamps, one set for each of said unattended o'ices and each setincluding alamp for each signal which may be received ,from thecorresponding unattended office, means individual to each set ofgas-filled discharge lamps for operatively connecting said lamps to saidsignal receiving means, thereby to effect the energization of the lampcorresponding to the condition existing in the unattended cnice to whichthe signal receiving means is then connected.

22. In a telephone system, an attended oflicev Ya plurality ofunattended oiiices, each comprising lines including a trouble checkingline and switches for seizing called lines, trunks between said attendedand each of said unattended ofiices, signal receiving means in saidattended ofce, means including said trunks and switches for connectingsaid signal receiving means to said trouble checking lines, one at atime, like vsignal 17 sending means in each of said unattended officesassociated with said trouble checking lines respectively, each of saidsignal sending means com prising a transformer, a plurality of sourcesof alternating current each of a different frequency, a plurality ofalarm relays each operated when a different trouble condition exists inthe oice in which the alarm relays are located and means including saidrelays for connecting one of said sources to said transformer when notrouble condition exists in the oice and for connecting another anddifferent one of said sources to said transformer when each differenttrouble condition exists in the cnice, means responsive to seizure ofsaid trouble checking line for completing a connection from said linethrough said transformer to one of said sources according to what if anytrouble then exists in the oice, thereby to selectively transmit to saidsignal receiving means a signal indicative of the condition existing inthe cfce, said signal receiving means comprising a plurality of relaysone for each diierent 18 signal which may be transmitted from the signalsending means of a connected one of said troulilcI checking lines, ltersfor selectively transmitting current of a dierent one of saidfrequencies to each of said relays respectively, sets of gas-lleddischarge lamps, one set for each of said unattended offices and eachset including a lamp for each signal which may be received from thecorresponding unattended office, means individual to each set ofgas-lled discharge lamps for operatively connecting said lamps to saidsignal receiving means, thereby to eifect the energization of the lampcorresponding to the condition existing in the unattended office towhich the signal receiving means is then connected, and means individualto each set of lamps for maintaining the energization of any lamp in theset for a predetermined interval after the connection of said signalreceiving means to the trouble checking line in the correspondingunattended office is ended.

HARRY H. SCHNECKLOTH.

